1. Field of the Invention
The invention relates generally to apparatus for pressure testing a specimen, and more particularly to cyclical pressure testing apparatus utilizing a first fluid to pressurize the specimen and a second fluid to pressurize the first fluid.
2. Reference to Prior Art
A prior art pressure testing apparatus includes a hydraulic pressure unit for cyclically supplying pressurized oil to a fluid separator including a diaphragm separating the oil from water on the other side of the diaphragm. The pressurized oil acts through the diaphragm to cyclically pressurize the water which is supplied to one or more test specimens to thereby subject the test specimen(s) to alternating high and low pressures. Since only the diaphragm separates the oil and water, seepage of fluids across the diaphragm results in cross-contamination of the fluids. In the event of a leak in a specimen, a water make-up pump supplies water to the specimen through a check valve to make up any water loss. This arrangement continually subjects the test specimens to the back pressure of the water pump such that the minimum test pressure is governed by the head developed by the water make-up pump.